I had a college professor who claims to have done something similar, except for FM radio. He had a neighbor who would blast his car radio while working in his driveway. The prof hooked up an RF oscillator to a directional antenna and aimed it at the car. With a little fiddling he found the broadcast frequency and was able to overload the AGC in the tuner so that the FM signal got attenuated to near zero.
Not sure if the story was true, but it seems feasible…
In the more general case, there’s jamming and there’s jamming. And i guess there’s also jamming. Seems like intentional targeted jamming has been answered by now. Transmitting a useful signal that stomps on others is the same principle, even if you are broadcasting your own personal music radio instead of electrical noise. Either way tne FCC is not happy. Ham radio has events, ‘fox hunts’, Wiki where one person sets up a beacon and everyone else uses triangulation etc to track it down - I’ve been told the FCC sometimes asks them for help tracking down illegal sources.
Then there’s your unintended consequence jamming. A microwave is leaking at 3 Ghz, something plugged into your house electrical circuit is putting noise on the power line that leaks onto your tv antenna and killing tv reception, one of your coworkers didn’t design in enough shielding or made …. Poor… choices for their power supply components. A lot of electronic devices have statement in the manual a la “this device will not emit harmful interference, and will safely handle any incoming interference “. Your design emits enough Rf to mess with other electronics, bad. Someone points an antenna, your device overloads and starts smoking, bad. Someone points an antenna, your device shuts down and reboots, acceptable. Someone points an antenna, your device doesn’t notice, you must have expensive and/or milspec equipment.
The other big one is structural “jamming” , which can be a reality behind hotel conspiracy theories. Build a nice large wood, concrete, and rebar object, sometimes called an “office building”. All that material will attenuate any signal, so some parts of the building become rf “dead zones”, no cell phone reception much less wireless data. Also really common in hospitals, my best guess is extra metal piping for oxygen and air supplies, extra wiring for all the power outlets each room needs, etc. This can be a safety issue if a fire fighter can’t communicate by radio in there. Good practice is to install repeaters that, say, receive the signal at an antenna on the building outside, then either amplify the signal or send the signal over wires to an antenna in the dead zone. Just because emergency services can communicate, doesn’t mean the hotel or hospital has to let everyone else use the repeater. So theory of “they be jamming us”, reality could be “they aren’t letting us use the hardware that lets ‘the man’ get any bars at all”.
Hotels jamming wifi definitely happened:
I know of one case where a small manufacturer was using an RF oven, basically a large microwave used to heat parts, and the shielding was leaking. No one, allegedly, at the company was aware of the problem but radio communication was disrupted for miles around. The feds tracked them down and the problem was fixed. No idea whether there were penalties.
The Marriott case was a legal decision, an application of the law as intended and written, but on moral grounds arguable either way.
Setting up your own wifi hotspot on the convention floor is jamming. There is only a limited number of wifi channels, and when lots of people set up their own wifi in the same space, none of it works properly.
Marriot was sending out ‘disconnect’ instructions to all the other wifi hotspots, which cleared up the spectrum and allowed wifi use. That was a public good, but had two problems: (1) They charged for it, (2), it wasn’t legal. The result is that, rather than using an automatic solution, they will have to walk up to every wifi hotspot, and tell the operator to switch off or leave. But that was going to happen anyway, because newer equipment doesn’t accept the ‘disconnect’ method they were using.
It’s not just Marriot that has a problem with this. Schools, Hospitals, Sports whatever. 10 years ago lots of people were moving infrastructure to WiFi, but when everybody has a wifi hotspot, that solution doesn’t work.
Several WiFI large systems have a jam feature - basically, disallow unauthorized WiFI extensions of the existing network. (I.e. you can’t plug your own WiFI hub into your office port so you can use your own signal). The “rogue hotspot” system simply sends a transmission to the WiFi if it detects a transmission. WiFi acts like ethernet - a device sends a signal packet, and if it detects another signal at the same time it will back off and try again. But repeatedly stomping on the rogue signal, the system can stop any connection to the rogue hub.
I believe they avoid the Marriot’s problem by ensuring the rogue hub is an extension of their own network, monitoring traffic on the network and also over the air to catch unauthorized signals.
Nowadays, most cellphones can be used as hotspots so it’s pretty much impossible to stop outside wifi signals and they may be legitimate uses of the technology. Can you tell the difference between stomping on Bob’s hotspot signal vs. the business next door?